Prior art air bags are made by mating a pair of plain weave fabric pieces coated or lined with rubber on the inner surface, joining them along the periphery with an adhesive, and stitching the adhesive-joined portions together, the air bags being referred to as plain weave type. However, when it is desired to accommodate air bags in narrow pockets as available in front pillar, roof side rail, center pillar, and quarter pillar zones, the prior art plain weave type air bags lack compactness due to the thickness of the stitched portion.
To combat this situation, JP-A 2-158442 proposes an air bag having a bag portion formed by hollow weaving, eliminating a need for adhesive bonds. This air bag is referred to as hollow weave type. The hollow weave type air bag is fully compact, but raises another problem. Because of the structure of the hollow weave type air bag, the rubber coating layer is applied to the outside surface of the air bag as opposed to the plain weave type. Then, upon inflation, the inflating gas acts on the bag from the base fabric side as opposed to the plain weave type where the gas acts from the rubber coating side. Although it is desired to ensure that the bag be kept inflated for a certain time, the conventional rubber coating composition used in the plain weave type fails to hold the same inflation time for the hollow weave type air bag.